1. Technical Field
The present invention concerns a slip ring transmitter and a method of reconditioning a slip ring transmitter. The present invention further concerns a wind power installation having a slip ring transmitter.
2. Description of the Related Art
Wind power installations are generally known and a typical installation is shown in FIG. 1. There the aerodynamic rotor rotates in usual operation relative to the stationary part of the pod, being driven by wind. To exchange electric energy or electric signals from the stationary part to the rotating part, namely the rotor, a slip ring transmitter is usually provided. In particular energy can be transmitted to so-called pitch motors which can adjust the rotor blades of the rotor in their angle of incidence. In addition for example energy can be transmitted for an electric blade heating system, if provided.
A particularity applies for gearless wind power installations which use an externally excited synchronous generator. In the case of such wind power installations an exciter current for producing an electromagnetic field in the generator rotor member is transmitted by way of the slip ring carrier or by way of a separate slip ring carrier. In that case current of high power, which can be several hundreds of kW has to be transmitted.
In particular the following three types of slip ring transmitters are known. The oldest option involves causing a carbon brush to rub against a corresponding contact ring to transmit the electric signal, whether it is an information signal or an energy signal, from the carbon brush to the contact ring or vice-versa. Such carbon brushes have become well-established and their properties are generally known. They are generally inexpensive but require regular replacement of the carbon brushes.
A so-called ‘gold wire slip ring transmitter’ is used to give an improvement. In that case a board having a large number of gold wires which basically project as in the case of a needle bed is guided on a corresponding slip ring which is electrically and mechanically matched to those gold wires. This gives in particular the advantage that a good contact property with a low level of abrasion wear is achieved by the choice of material, by using gold. Nonetheless with the passage of time deposits occur here at the positions of the respective gold wires, on the corresponding slip ring in grooves produced therein, in which faults can also occur, in particular in the gold layer. The slip ring usually comprises brass or a similar metal alloy provided with a gold layer in the contact region. Oil can be provided in the grooves for cooling purposes and for improving contacting. With a small amount of oil and/or a high degree of wear or in a severely worn condition the gold wire rubs against the slip ring and changes the surface there, which however can be difficult to detect. As a result the gold wire also suffers and wears away more quickly.
A so-called ‘multi-brush slip ring transmitter’ is proposed as a further improvement. In that case at least one bundle of many wires which are as fine as hairs runs against a corresponding slip ring. Such bundles or bunches of those many hair-fine wires are usually arranged, fixed and contacted on a circuit board and therefore reference is usually made here only to a circuit board, which includes the above-mentioned bundles or bunches. The circuit board thus forms a circuit board and is thus the counterpart to the slip ring against which it rubs. The circuit board can also be referred to as the brush. Those terms basically apply irrespective of the technology which is actually employed. Basically contacting occurs here on the basis of the principle that the wires can bear against the corresponding slip ring with little force and good contacting is effected simply by the large number of wires. That bundle is similar to a brush so that the term ‘multi-brush’ has also gained acceptance in German linguistic usage in the corresponding technical circles. Such a multi-brush technology can be handled in comparatively robust manner and avoids the above-described deposits involved in the gold wire technology and carbon abrasion in the case of carbon brushes.
A problem with the gold wire system is in particular that, besides the gold wires, the corresponding slip ring also wears. Deposits and defects occur on the slip ring, which in turn lead to severe wear of the gold wires. After corresponding wear therefore, in addition to the gold wire board with the gold wires, the slip ring also has to be replaced, which is complicated, expensive and thus undesirable.
The German Patent and Trade Mark Office searched the following state of the art in the priority application in relation to the present application: DE 24 58 991 B2; DE 10 2007 060 985 A1; DE 694 14 687 T2; U.S. Pat. No. 4,398,113 A and JP 2009-225578A.